1. Field of the Invention
The present invention relates to a light guide plate structure and a back light module, and more particularly to a light guide plate structure for improving scattering effects on a light scattering surface and a back light module applied therefrom.
2. Description of the Related Art
For the trend of small sizes of electronic products, the development of electronic devices is toward high density and integrity in small size electronic products. Because a variety of functions embodied within electronic products with small sizes, a large number of portable devices have been popularly used and replaced the big sized electronic products. Therefore, they have become the main stream in consumer market. These portable devices includes, such as notebooks, cell phones, electronic dictionaries, personal digital assistants, web pads, tablet PC and portable games.
For the application of small size electronic products, liquid crystal displays (LCD) with high efficiency of space, high quality, low power consumption and low or no radiation have been popularly used. LCD is composed of a liquid crystal panel and a back light module. Because liquid crystal within the panel does not illuminate itself, the back light modules must provide a plate light source for the panel. Then, LCD serves the function of display. Therefore, back light modules are very important in displays.
FIG. 1 is a cross-sectional schematic drawing showing a prior art back light module. Referring to FIG. 1, the back light module 100 includes a light guide plate 110, a linear light source 120 and a reflective cover 130. The light guide plate 110 is, for example, a plate-type light guide plate, which comprises at least one light incident surface 112, a light scattering surface 114 and a light emitting surface 116. The light incident surface 112 is on a sidewall of the light guide plate 110, the light scattering surface 114 is on a bottom surface of the light guide plate 110 and the light emitting surface 116 is on a top surface of the light guide plate 110.
The linear light source 120 is, for example, a cold cathode florescent lamp, which is disposed next to the light incident surface 112 of the light guide plate 110, wherein light from the linear light source 120 transmits through the light incident surface 112 and enters into the light guide plate 110, and the light scattering surface 114 passes the light to the light emitting surfaces 116 and out thereof.
Additionally, the reflective cover 130 is disposed next to the light incident surface 112 of the light guide plate 110 and covers the linear light source 120 for reflecting light from the linear light source 120 to the light incident surface 112 of the light guide plate 110.
Referring to FIG. 1, the light scattering surface 114 of the light guide plate 110 provides a enough scattering area. Therefore, light from the linear light source 120 after being scattered on the light scattering surface 114 can uniformly travel to the light emitting surface 116, and the light exiting form the light emitting surface 116 transforms into a plate light source. It should be noted that a plurality of transparent bumps 140 are disposed on the light scattering surface 114 as scattering spots thereof in prior art. The transparent bumps 140, however, are made of the same material of the light guide plate 110 and have the same refractive index as the light guide plate 110. Therefore, the scattering effect on the light scattering surface is limited.
FIG. 2 is a cross-sectional schematic drawing showing a prior art back light module. Referring to FIG. 2, a back light module 100′ has the same structure as the back light module 100 described in FIG. 1. The same descriptions will not be repeated herein. The difference between these two back light modules is that a plurality of holes 150 are formed on the light scattering surface 114′ serving as scattering spots thereon. However, in the prior art back light module light still transports in the same material. Therefore, the scattering effect on the light scattering surface 114′ is limited.
From the descriptions mentioned, the prior art back light module by forming either transparent bumps or holes on the light scattering surface of the light guide plate cannot provide excellent scattering effect and a uniform plate light source because of back scattering effects thereon.